1. Field of the Invention
Embodiments of the invention relate to a pneumatic vehicle tire having two or more bracing plies intersecting at an angle and with steel reinforcements and also having a bracing bandage of one or more plies and with reinforcements.
2. Discussion of Background Information
Structures of pneumatic vehicle tires are sufficiently well-known to a person skilled in the art. Radial tires include a belt and often a bracing bandage.
The belt consisting of two or more bracing plies intersecting at an angle provides the stiffness of the tread in the longitudinal and transverse directions. This serves for force transmission during driving, improves the lateral guidance and reduces the abrasion of the tire. The bracing bandage, consisting of one or more circumferentially oriented plies, mainly serves for additionally absorbing forces in the circumferential direction, in order for example to limit the expansion of the tire caused by centrifugal forces during the operation of the tire. The bracing bandage may cover the belt, or else the bracing bandage as a whole or individual bandage plies may be located between or under the bracing plies.
It is known and customary at present to use steel cords as reinforcements in the bracing plies of the belt. The steel cords are arranged within the reinforcing ply substantially parallel to and at a distance from one another and are embedded in rubber material. Bracing plies fitted in passenger car tires often have steel cords of the structure 2×0.30 mm, for a setting of 80 epdm (ends per decimeter) or more. The cord structure 2×0.30 mm means that two wires (filaments) of 0.30 mm in diameter are twisted together to form one cord, so that the cord has a diameter of about 0.60 mm. The cords of this diameter are embedded in rubber to form plies. The greater the cord diameter, the more rubber is required for embedding the cords and the heavier each bracing ply is, and the heavier the tire. A prescribed bracing ply is constructed in such a way that, under a predetermined extension of 1%, it has a tension of greater than 17 500 N per decimeter (dm) of width. A disadvantage of bracing plies with the aforementioned steel cords is that they are comparatively heavy in terms of weight and expensive in terms of material.
It is likewise known and customary at present to use bracing bandages in combination with steel belts. Bracing bandages fitted in passenger car tires often have one or two plies of rubberized nylon cords of the structure 940×2 for 80 epdm. Such a bracing bandage is constructed in such a way that, under a predetermined extension of 1% in the direction of the longitudinal extent of the cord, a force of less than or equal to approximately 1500 N per dm of width builds up. Nylon is often used because this material has a heat shrinkage, that is to say it shrinks when heated. This is of advantage both during the vulcanization of the tire and during operation at high speed, because the bracing bandage then helps to hold the belt assembly together. Furthermore, this prevents the bracing bandage from undergoing compression during operation, which is disadvantageous for its fatigue strength and can lead to ruptures of the bandage material.
Efforts in tire development are constantly striving to achieve a low-cost tire of low weight, with which however the performance is maintained at a high level.